Northerner I know It's kinda cheap for it's tier, but we're talking about tier 13: 10-20 million is a very large price range.
Perhaps the Overseer isn't good enough alone, it certainly works if there are other ships to distract.
There are two battles I checked, against Invictus (which turned out to be not so invincible as the name suggests)
And Megalodon, which did some evil decapitation move I will not talk about in depth...
(Wait, I left the fight against Megalodon running for a while, and noticed this...)
(Now, I'm surprised that two Overseers could take it down while the large railgun ship was made useless in the first seconds.)
Alpha (Megalodon is quite weak against multiple ships at once. And ships with decent pd/flak defense. Guess I could achieve the same result with three manually piloted Castle Archers...)
Alpha Passed! I really like this design! Plenty of fire power and two big ion ships! whats not to love?
CursedPh4nt0m No I think that you posted that ship before... or at least one very similar to it. Which did pass.
(But I re-named it)
Northerner Yeah, that's the ship I was referring to:
CursedPh4nt0m It's a (rather cheap) copy of my tier two ion ship
This new one is in tier one and I obviously had to change some stuff to get it there. It's nice you consider it good enough to make it into the mod without testing, that somehow feels like cheating tho.
And you're free to give them actual names. I'm terribly uncreative and usually struggle more with giving the ships a fitting name than actually building them. 
Also: 'Castle Archer V6'
A bunch of tweaks here and there...
CursedPh4nt0m Did not pass. It was really close however! It went 5-5 in its tier (which does not pass) If anything I would remove of some of the armor that doesn't really benefit the ship and add a small laser.
Northerner (Almost expected that much...)
I'd assume this version got higher chances then:
CursedPh4nt0m Passed! Adding that laser was just enough to get it to pass! if you are interested it passed 6-4
Northerner I've gotten someting in tier one; my life's complete now.
(Next are some ships for the higher tiers, that hopefully goes better. And I still have to (learn to) paint my submissions, now that I think about it...)
You know its been too long since i last did something here... time to work...
Borg Assimilated Cruiser
Cost: 11.9M
Ah making somewhat effective ships is hard with all the new weapons such as the electro missiles and stuff...
(Doubt it will pass.. ._.)
Also this is probably the first ship ive posted that aint the same on both sides... oh well
Borg Probe
Cost: 1.4M
(yes i may be nerding out on star trek borg....
The_Bloodnaught That's actually a borg probe.
RedAndCosmoteer Now all you need is the Borg Cube.
Hi, after some work, I managed to make bigger and stronger version of my missle + railgun destroyer. Stands against most of tier 10 ships quite well.
MR Destroyer II
Tier 10
Cost: $4,99 mill
Edit: Implemented few CursedPh4nt0m's advices.
Zachary No, then there's the borg Sphere.
And the Tactical Cube.
Krowanek Nice ship! Fighting this with something slower must be really hard...
I see some room for improvement however:
Use 1*2 armor for the hull, it's got higher penetration resistance.
Replace those connecting corridors with structure. It may look worse, but only costs half as much.
Add a second railgun, your current power system can already supply two anyways.
Remove some unnecessary corridors (like the ones in the inner flak module).
One factory can't even supply a single flak turret, so having it supply two is a rather bad idea.
Remove some of the frontal amor, your never gonna need that much.
You missile modules could have two shields.
Check for those little mistakes everyone makes once in a while. (The second shields in front of the railgun lack armor on the inner side, the door placement could be improved on some spots, ....)
CursedPh4nt0m Didn't know 1*2 armors are more resistant, thx. I was messing around with second railgun and double shields on missle modules, but as I was trying to maintain the look while still staying under 5 mill, they just didn't fit. Maybe i'll try to make another version of it later. Also didn't know (and didn't check it either) that flaks use so much ammo.
This build isn't most efficient for sure, it's more about look, but still being able to fight against GiF ships in its tier as that was my goal.
Northerner Nuke ships are not so easy to work with, the AI is not so smart at times...
Nevertheless, I think I got something working.
(Thanks @CursedPh4nt0m for alerting me about that door!)
Cinder
I won't be surprised if it doesn't pass, but I feel like getting a nuke ship in is something I need to get done. 
